Vehicle braking/driving force control device

Abstract

An ECU calculates the thermal margins of the in-wheel motors, on the basis of the thermal capacities of the in-wheel motors, the allowable limit temperatures, and the motor temperatures. Next, the ECU distributes the total requested torque between the requested torques for each wheel using the percentages of the thermal margins. The ECU controls the operation of an inverter such that the in-wheel motors generate the requested torques for the wheels. Thus, the four in-wheel motors generate uniform amounts of heat.

Description

TECHNICAL FIELD[0001]The present invention relates to a vehicle braking / driving force control device for controlling a driving force or a braking force to produce with each wheel of the vehicle individually.BACKGROUND ART[0002]As one form of electric cars, an in-wheel motor type vehicle in which a motor is arranged in or around the wheel placed under the vehicle body spring and drives the wheel directly is developed. In the in-wheel motor type vehicle, it is possible to control the driving force or the braking force given to each wheel independently depending on the traveling condition of the vehicle by an independent drive (power running) control or an independently regenerative control of a motor provided to every wheel.[0003]Because a motor is arranged in or around the wheel in such an in-wheel motor type vehicle, generated heat by the braking / driving movement of the motor is hard to be emitted and the motor is easy to be full of heat. Thus, for example, in the driving force cont...

AI Technical Summary

Benefits of technology

The invention aims to prevent overheating of the in-wheel motors in electric vehicles and to maintain good stability and performance during travel. The invention achieves this by averaging the temperature of each motor and distributing the driving and braking force between the front and rear wheels based on the load balance. The invention also adjusts the distribution based on the thermal margin balance to ensure a good stability of the vehicle at low speeds. This helps to prevent premature failure of the motors and ensures a consistent and reliable driving experience.

Problems solved by technology

However, in the driving force control device proposed to Patent Literature 1, the distribution change of the braking / driving force responded to the heat generation state of the motor is not performed at all in the period when it is not estimated that motor temperature will exceed the permission limit temperature, and the braking / driving force of the motor is limited at the point in time when it is estimated that the motor temperature will exceed the permission limit temperature.

Therefore, during the period until the point in time, a big difference occurs in the use situation of each motor, and the heat generation state of each motor becomes imbalance, and a motor with enough thermal margins is mixed with a motor with a little thermal margins.

Thus, because thermal margins of each motor may become imbalance, only one motor may reach the permission limit temperature at an early stage.

In this case, because the braking / driving force of the motor will be limited from the point in time, the control property of the yaw rate or the lateral acceleration that can occur in the vehicle may decrease.

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